Ultrasonic phased array (later as “PA”) instruments provide a significant advantage for many applications because they display a cross section of the region being inspected, thereby facilitating the visualization of an imperfection, its feature, location and size, typically sought by ultrasonic inspection. Another significant advantage of ultrasonic phased array instruments is that they provide much higher inspection speed and therefore higher productivity in comparison to single element probe systems.
For inspecting a pipe during production, typically a PA system includes a linear phased array probe installed in parallel with the longitudinal axis of the pipe. The PA probe moves and scans circumferentially around the pipe. The relative circumferential movement is encoded to enable C-Scan production. Sizable imperfections that such PA systems target include longitudinal, transverse and oblique cracks that are located at either the inside diameter (ID) or outside diameter (OD) of the pipe.
The typical pipe inspection using PA systems uses a widely known standard given by American Petroleum Institute. Specifically related to defect sizing, the widely used and recommended practice is given by Recommended Practice for Ultrasonic Evaluation of Pipe Imperfections—API Recommended Practice 5UE 2nd Edition, June 2005—Addendum 1, APRIL 2009 8.2.2 page 7—Amplitude Distance Differential Technique (Later as ADDT). According to ADDT, “The ADDT is based on the premise that the radial depth or thickness of an imperfection affects both the amplitude of the received echo signal and the differential time of flight of the transmitted ultrasonic wave as it passes over the imperfection. ADDT relates to the loss of signal amplitude, relative to the time (distance), as the ultrasonic beam is moved over the imperfection. The amount of time (distance) to incur a 50% drop in amplitude of the returned signal is related to the depth or thickness of the imperfection.” A discussion of the ADDT method can be found in reference material ADDT, which is herein incorporated by reference.
One drawback brought by the method mentioned in the above ADDT is that the process is completely manual, comprising at least six steps to be performed for calibration and six more steps for inspection. More specifically, the existing practice has to re-orient the probe manually after a possible indication is found, to make sure the probe is scanning the pipe perpendicularly to the indication. This will take at least one more pass of scanning. However, using PA system wherein PA probes are usually placed to scan the pipe circumferentially and the probes could be in any orientation relative to the unknown indications. It would be desirable to achieve a method so that, in one pass of scan, the indication can be both found, sized and accurately located without having to re-scan with re-oriented probe.
Another existing effort is seen in U.S. Pat. No. 7,240,554 which describes a variation of the ADDT measurement method, adding mechanism achieving a semi-automation for the process. It teaches the use of an A-Scan envelope to keep track of the maximums of one pass inspection over the indication that is perpendicular to its length.
Although both methods stated above permits to size longitudinal, transversal and oblique imperfections manually or semi-automatically, they are rather slow and heavily dependent on user's interaction or operation.
Therefore, it is needed and desirable to provide a system capable of providing size information of all directions during a pipe inspection with a one-step calibration and inspection.